The invention relates to a method and apparatus for foming cants slabbed on four sides from logs. In the trade today, the common manner of forming cants is to pass a log through a set of saws, slabbing two sides thereof, and then taking a log and passing it through the saws again to slab the other sides of the log. Any adjustment to the spacing of the saws is made by rotating a hand crank to slowly and incremently move the saws toward and away from each other. Such common procedures is the trade are inefficient, very labor-intensive per unit of production, and are not capable of achieving high rates of production. There have been proposals (see U.S. Pat. No. 2,669,262) for forming cants automatically utilizing a single machine by mounting pairs of saws on a moveable carriage, and moving the carriage back and forth across a bed for supporting the saws while moving the logs and partially-slabbed cants from one position to another. However, such proposals have not met with widespread industry acceptance, perhaps because of the difficulty of mounting two pairs of saws on a moveable carriage and properly controlling the movement of the logs from one position to another.
According to the present invention, a method of forming cants slabbed on four sides at a high rate of production, and a sawmill assembly for practicing the method, are provided which overcome the problems inherent in prior art arrangements. According to the present invention, a method of forming cants slabbed on four sides from logs, utilizing first and second in-line sets of pairs of saws, is provided. The method comprises the steps of feeding a log to the first set of saws in a given generally horizontal direction, the first set of saws slabbing two opposed sides of the logs; continuing feeding of the log from the first set of saws to the second set of saws substantially in said given horizontal direction, and rotating the log 90.degree. about an axis along said given horizontal direction during feeding from the first set of saws to the second set of saws; and slabbing two opposed sides of the log with a second set of saws after 90.degree. rotation of the log, to form a cant slabbed on four sides. The log is positively guided into engagement with both the first and second sets of saws, and is positively held down during cutting for safety and in order to effect clean cutting. The scrap formed by the slabbing is automatically conveyed from the saw sets in substantially the same direction as the log moves, to a disposal area. The distance between the pairs of circular saws in both the first and second saw sets is adjustable in the generally horizontal dimension transverse to said given direction by effecting automatic detented adjustment of the distance just prior to the log being received thereby. An operator watching the log being fed to a given saw set by eye guages the approximate dimensions of the log, and then pushes a button automatically moving the saws to a particular detented position desired, depending upon the log size. In this way, there is a minimum of waste while high rates of production can still be achieved.
The sawmill assembly according to the present invention comprises a pair of circular saws rotatable about a common horizontal axis and spaced from each other along the axis, said saws comprising a first set of saws, and a second set of saws being provided substantially identical to the first set of saws. A frame assembly mounts the first and second saws substantially in a generally horizontal dimension generally transverse to the axis of the first and second saw set pairs, and means are provided for feeding an article to be cut to the first saw set for feeding an article to be cut from the first saw set to the second saw set, in each case a main portion of the article passing through the space between the saws while side portions of the article are separated from the main portion. Additionally, means are provided for facilitating the rotation of the article 90.degree. about an axis along said horizontal dimension, said facilitating means being disposed intermediate the first and second saw sets.
There are provided means for mounting the saws of each of the first and second saw sets for axial movement along the axis of rotation thereof, the power means associated with each saw set for effecting automatic detented adjustment of the distance between the saws. A first control panel is mounted adjacent the first saw set, and a second control panel is mounted adjacent the second saw set, the panels including the control means for operating the power means of the first and second saws respectively.
The means for facilitating the 90.degree. rotation of each article comprises a plurality of powered screw rollers each rotatable about an axis parallel to the axis of rotation of the saws. A pair of guide walls mounted on the frame assembly are disposed vertically above and along either side of the powered screw rollers, and are elongated in said generally horizontal dimension. Centering means are disposed on both the upstream and downstream ends of the guide walls for centering the article as it enters and leaves the area defined by the guide walls. An operator standing at the rotation means waits until the log is substantially on the screw rollers, and then rotates the log 90.degree. so that it turns and lays on one of the slabbed sides thereof, and then proceeds from the rotating means toward the second saw set.
The articles are fed through the sawmill assembly by a toothed chain conveyor running in channels, or between channel surfaces, extending substantially the length of the frame assembly. The toothed chain passes under the screw rollers and then returns to its original position, whereby the same chain conveyor can move the article being cut through the first set of saws and the second set of saws. Also, the powered screw rollers facilitate feeding of the partially slabbed log from the rotation facilitating means to the second saw set. A pair of scrap conveying conveyor belts are disposed outside of the saw sets and the rotation facilitating means, and may be powered by the same motor that powers the chain conveyor.
The articles to be acted upon by the sawmill assembly are indexed one at a time to the channel before the first saw set, to be ultimately engaged by a tooth of the toothed chain conveyor, in a direction parallel to the axis of rotation of the saws. Indexing means for accomplishing this comprise conveying means disposed vertically above the channel for conveying articles toward the channel, arm means disposed between the conveying means and the channel rotatable about an axis parallel to said generally horizontal dimension; and power means for rotating the arm means for engaging a single article on a conveying means and depositing it in the channel while simultaneously preventing movement of further articles on the conveying means toward the channel.
It is the primary object of the present invention to provide a method and apparatus which form cants slabbed on four sides in a simple manner, yet at a high rate of production. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.